The present disclosure relates generally to particulate monitors and smoke detectors, and more particularly, to an optically enhanced protective cover for a chamberless sensor.
Smoke detectors play an important role in identifying smoke, ideally alarming as early as possible in the course of fire. Smoke detectors can use one or more sources of light as the source of the smoke detection scheme, and can use multiple wavelengths of light to help improve detection performance. For example, dual wavelengths of light, one being infrared and the other being visible, can be used in a smoke detector. A chamberless detector can provide improved sensing performance over designs that utilize a chamber, therefore resulting in the popularity of the chamberless design in high-performance applications. A chamberless detector can be referred to as a next-generation point sensor, because of its advanced design and its use in detecting smoke at a particular point of installation. A chamberless detector can also be referred to as a chamberless point sensor.
A commercial aircraft is a non-limiting example of a high-performance application where a chamberless point sensor utilizing multiple wavelengths of light can be used. There are many factors that contribute to the need for a high-performance chamberless detector, with non-limiting examples including the desire to discern between steam or dust and the smoke particles from a fire, the desire to avoid nuisance alarms from food preparation, and the desire to detect smoke particles that can be produced from smoldering synthetic materials, often resulting in particle sizes smaller than 0.5 μm (microns) in diameter. Additionally, chamberless detectors utilizing multiple wavelengths of light can be used to monitor indoor air quality, where the presence of fine particles (particle sizes ≤2.5 μm) and coarse particles (particle sizes ≤10 μm) can be important.
A protective cover can be positioned on a chamberless detector to overcome some of the problems that have been associated with chamberless detectors, for example, there not being a well-protected volume that is free from interference or tampering. Typical examples of a protective cover can include a clear or opaque cover, which can also include apertures. While a protective cover can be helpful in reducing interference from ambient light sources emanating from the surrounding environment, there can still be problems with the transmission, reflection, and/or absorption of light by a protective cover.